Hydrogen sulfide and its donors: Novel antitumor and antimetastatic therapies for triple-negative breast cancer.

Hydrogen sulfide (HS) is considered as a novel second-messenger molecule associated with the modulation of various physiological and pathological processes. In the field of antitumor research, endogenous HS induces angiogenesis, accelerates the cell cycle and inhibits apoptosis, which results in promoting oncogenesis eventually. Interestingly, high concentrations of exogenous HS liberated from donors suppress the growth of various tumors via inducing cellular acidification and modulating several signaling pathways involved in cell cycle regulation, proliferation, apoptosis and metastasis. The selective release of certain concentrations of HS from HS donors in the target has been considered as an alternative tumor therapy strategy. Triple-negative breast cancer (TNBC), an aggressive subtype with less than one year median survival time, is known to account for approximately 15-20% of all breast cancers. Due to the lack of approved targeted therapy, the clinical treatment of TNBC is still hindered by metastasis as well as recurrence. Significant efforts have been spent on developing novel treatments of TNBC, and remarkable progress in the control of TNBC by HS donors and their derivatives have been made in recent years. This review summarizes various pathways involved in antitumor and anti-metastasis effects of HS donors and their derivatives on TNBC, which provides novel insights for TNBC treatment.